One risk of saying that expressions are "unlikely to have any practical
use" is that sophisticated programming evironments tend to be used to
automate tasks that are relatively unrestricted.
Perhaps no human using Mathematica would type in these expressions by
hand, but it is certainly conceivable that someone might develop an
application package that would end up generating forms like these as
intermediate steps while addressing very sensible and practical
problems.
Think of something like a C language compiler: it is clear that C
compilers will, even for simple, straightforward C expressions,
generate machine code that is quite unlike what a human machine code
programmer would create. If a CPU acted strangely because its designer
never anticipated codes in these orders, people would complain that the
CPU has bugs. Perhaps compiler writers would learn to work around these
bugs, if they were isolated and predictable enough, but these would be
bugs nonetheless.
People trying to build large systems need building blocks that are
*robust*, in the sense of behaving predictably *even in situations that
might not be forseeable*.
You might get a warm fuzzy feeling from experimentation and discovery,
but people using libraries will end up performing mysterious
uncontrolled experiments, not of their own choosing, and perhaps
silently returning bad results.
--Joe